The Hybridoma Facility of the Laboratory of Cellular Physiology collaborates with numerous laboratories in FDA, NIH and other institutions in the production and characterization of monoclonal antibodies (MAbs). During this reporting period, the Facility has initiated and/or completed fourteen hybridoma fusions, four related procedures from previously completed fusions and two extended runs for production of MAb containing culture supernatant in a hollow fiber bioreactor. These fusions required screening by ELISA or Western blot of approximately five thousand wells of culture supernatant by the facility or its collaborators. As a result over three hundred lines have been selected for further study and consequently expanded in order to allow for frozen storage. These fusions included a procedure where spleens of animals immunized with two different antigens were fused in parallel. Three fusions were adopted to incorporate immune lymphocytes from the lungs of mice immunized with B. pertussis organisms or components by aerosol. Reagents produced in this facility have been used in six of seven DBP laboratories and have had a significant impact on research projects and regulatory matters.